Recently found installers problem with new MacPro (Dual Xeon 3gHz) reported by different people.
Symptoms: Installing applications problem. When you running installers that requires user authentication, you will get message about insufficient privileges even you logged in as admin account or single user on comp. When trying to update Mac`s firmware no react for Shutdown button, while "Cancel" works and aborting process so you`re unable to update. And some other processes those requires user login confirmation or authorization.
Problem: Pre-installed version of Tiger is wrong for this Mac.
Solution: You must reinstall OS X form disks supplied with this Mac Pro. You may choose install with preserving user data and setting. Erasing not necessary. After succesfull reinstalling system, first download firmware update, update your firmware (if it will work fine it will confirm that everything now works correctly). Then you may download and apply all available updates for your OS.
P.S. Was hard to define problem because everything seems to work unless you try to install something (especialy with VISE (TM) installers. Strange, but even in this situation some installers works- at least Adobe CS2 installs with no problems.
I hope it works for you! Good Luck!